HackerEarth Rotation problem solution

In this HackerEarth Rotation problem solution You are given two strings S and T of the same length N. Your task is to convert the string S into T by doing some operations. In an operation, you can delete the first character of the string S and append any character at the end of the string. You are required to determine the minimum number of operations to convert S into T.

HackerEarth Rotation problem solution.

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define mod 1000000007ll
#define vll vector<ll>
#define pll pair<ll,ll>
#define vpll vector<pll>
#define pb push_back
#define mp make_pair
#define x first
#define y second
ll lps[1000005], match[1000005], n;
string s, t;
void com_lps()
{
  ll j = 0, i = 1;
  lps[0] = 0;
  while(i < n)
  {
    if(s[i] == s[j])
    {
      j ++;
      lps[i] = j;
      i ++;
    }
    else
    {
      if(j)
      j = lps[j - 1];
      else
      {
        lps[i] = 0;
        i ++;
      }
    }
  }
}
ll solve()
{
    memset(match, 0, sizeof(match));
  ll  i = 0, j = 0;
  while(i < n)
  {
    if(t[j] == s[i])
    {
      j ++;
      match[i] = j;
      i ++;
      if(j == n)
      return 0;
    }
    else
    {
      if(j)
      j = lps[j - 1];
      else
      i ++;
    }
  }
  return n - match[n - 1];
}
int main()
{
//  freopen("inp.txt", "r", stdin);
//  freopen("out.txt", "w", stdout);
  cin >> n;
  cin >> s;
  cin >> t;
  com_lps();
  cout << solve();
//  fclose(stdin);
//  fclose(stdout);
  return 0;
}

Second solution

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = 1e7 + 17;
int main(){
  ios::sync_with_stdio(0), cin.tie(0);
  int n;
  cin >> n;
  string s, p;
  cin >> s >> p;
  reverse(s.begin(), s.end());
  for(int i = 0; ; i++){
    if(string(s.rbegin(), s.rend()) == p)
      return cout << i << 'n', 0;
    s.pop_back();
    p.pop_back();
  }
}

coding problems solutions